Orange Pistons

[Signature620]

I've got the head off of a cm871 because it has a leaking #4 injector sleeve. It's done 900,000km. Spent most of it's life deleted but has had a variety of cals through it. The last 1.5 years it's had a 600hp cal with safe timing and a Holset HX60 fitted. Everything has been fine until the fuel/coolant cross contamination.

Upon removing the head, I notice the rear 3 pistons are orange when wiped and the front 3 are just covered in a light carbon. It runs rough intermittently at idle but fine at any other speed.

Timing actuator perhaps???

   

   

[smorgan87]

Stained by coolant?

[Rawze]

definately some kind of staining of sorts.

are those oe pistons? - kinda look like the coating is missing, hard to tell.

[Unilevers]

i see you must be running right on the edge of the timing limit, i would even back it off a few degrees you can see the spray pattern is pretty high in the bowl.

[Signature620]

All genuine parts Rawze.

Do those spray patterns stay there long term? Before it came apart I drove it for 3hrs with a leaking thermostat and it didn't get hot enough to move out of the cold start/warm up mode.

[Rawze]

(02-06-2019 )Signature620 Wrote:  All genuine parts Rawze.

Do those spray patterns stay there long term? Before it came apart I drove it for 3hrs with a leaking thermostat and it didn't get hot enough to move out of the cold start/warm up mode.

Well, the second picture (not the orange one) looks like there was some smoke buildup (grey-ish color), and some slight hints of NOx gas buildup on the edges of the bowl in a few places. It is a sign of it running as lean as someone could get away with. - I would say to back off the boost pressure a psi or so + injection timing about 1-2 degrees in the working regions if someone have boroscoped it and it looked like that just for protection. A Uni pointed out, the spray is right at the top edges of the bowl too. You can usually get away with that, but it olny takes a bad spray nozzle on one injector to push it over the limit and cause a piston issue when running it at the top edges like that. - I run mine there, but i use reduced HP (450hp/1750trq) and never drive hard. That is how I get away with it on mine. A hard working engine, it could be a bit risky, just saying. On a hard working engine, big hp, you would want it not quite as clean running, to the point of seeing occasional smoke puff when getting on it hard while the turbo caught up.


That is my 2-cents on it base on a very limited view of only a picture or so. If i were standing over the engine and looking at the whole thing, liners, under side of head, etc. it would likely be more revealing.

[Signature620]

Here's the head. I've just wiped it to get the oil off - Some of the light buildup on the valves came off on the rag.

There's definately something happening with the rear bank.

   

EDIT: I removed and checked the timing actuators - Both have about 0.002" of play but the rear one has a significant step in it when I move it in and out.

[Rawze]

(02-06-2019 )Signature620 Wrote:  Here's the head. I've just wiped it to get the oil off - Some of the light buildup on the valves came off on the rag.

There's definately something happening with the rear bank.



EDIT: I removed and checked the timing actuators - Both have about 0.002" of play but the rear one has a significant step in it when I move it in and out.

front 3 look pretty good. rear 3, yeah, you can see somethng going on. - i would replace the timing actuator on it just to be safe. Also make sure the engine brake solenoid for the back 3 is not getting sticky or something.

[redbeard]

Absolutely love this kind of discussion. Please keep it up boys